Attendance at Conservative Temple

I am a lifelong Conservative Jew and I am a member of a Conservative Temple since birth where I was once the president. I know very little about Orthodox Judaism. For the first time in my life, I went to an Orthodox synagogue for a bar mitzvah last week and I did not like having to sit separately from my wife and daughters. I had heard of but never seen anything like that in person before. I asked the rabbi there why the genders sit apart, and he gave me an explanation. He told me that one who attends a service at a Conservative Temple not only does not fulfill the mitzvah of attending Shabbat services, but is also violating 23 negative commandments in the Torah. He didn’t tell me which ones. What 23 negative commandments could one possibly be violating by attending a Conservative service?